feat: add log date timezone

[liuzhenghua]

Description

add log date timezone.

Fixes # (issue)

Type of Change

Please delete options that are not relevant.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update, included: Dify Document
• [ ] Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement
• [ ] Dependency upgrade

How Has This Been Tested?

add env LOG_TZ=Asia/Shanghai, log date time would be changed to GMT+8

• [ ] TODO

Suggested Checklist:

• [x] I have performed a self-review of my own code
• [ x] I have commented my code, particularly in hard-to-understand areas
• [ ] My changes generate no new warnings
• [x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods
• [ ] optional I have made corresponding changes to the documentation
• [ ] optional I have added tests that prove my fix is effective or that my feature works
• [ ] optional New and existing unit tests pass locally with my changes